A.W.R. wrote:

Shaped charges using normal explosive via explosions perpendicular not
behind path of travel "fingers on watermellon seed" squirt a molten
bunch of formerly solid materials to 6 - 10 km/s. Not efficient I
think, but maybe benefits make it worth it.

Nope.

Several problems.
The control is very poor, and will only give approximate direction.
The accelleration is rather high, so you can only put in basically bulk
materials.
What you shoot has to be very strong, and temperature resistant.
It's a very inefficient way of launching - you use far more mass of
explosive than you'd use rocket propellant.
You can't shoot anything through atmosphere at these speeds (well,
nothing smaller than many tens of meters in size), so you need to launch
all the explosive into orbit first.
In balance, it's not worth it, as it much heavier, and much less flexible
than rockets.